Conveyer for bakers&#39; ovens



K. D. LoosE Er- AL Oct. 14, 194,7.

CONVEYER FOR BAKERS OVENS origimalv Filed July 19, 1940 1::

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Oct. 14, 1947. K. D. LoosE ET AL 2,429,100

CONVEYER FOR BAKERS? OVENS original Filed July 19, 1940 e sheets-sheet 28 SheefS-Sheet 3 Oct. 14, 1947. K. D. Loose Er AL coNvEYER FOR BAKERSovENs original vFiled July 19., 1940 Oct. 14, 1947.

Original Filed July 19, 1940 l K. D. LOOSE El' AL CONVEYER FOR BAKERSOVENS 8 Sheets-Sheet 4 'A NVENTORs I N w "1mm Oct. 14,1947.' K. D. LoosEET A L l 2,429,100

GoNvEYER FOR BAKER'S' ovENs Original Filed Ju1y`l9, 1940 8 Sheets-Sheet5 VENTO BY I ji Z ATTORNEY K. D. LoosE ET AL V2,429,100 coNvEYER FORBAKERS vENs Original Filed July 19, 1940 8 Sheets-Sheet 6 |N v N o WMMATTORNEY @www Oct. 14, 1947.

K. D. LosE x-:r Al. I 2,429,100

Oct. 14, 1947.

OVENS CONVEYER FOR BAKERS Aoriginal Filed July 19. 1940 8 Sheets-Sheet'7 iNvEf-OZS mada@ ATTQRNEI S NNN Oct. 14, 1947. K. D. LoosE ET ALCONVEYER FOR BAKERS oVENs Original Fild July 19, 1940 l8 Sheets-Sheet 8l v N'rRS BY 9m ATTORNEYS All III! IH Patented Oct. 14, 1947 UNITEDSTATES PATENT GFFICE CONVEYER FR BAKERS OVENS Kenneth D. Loose,Bronxville, N. Y., and Charles W. Watkins, Dayton, Ohio, assignors toLoose- Wiles Biscuit Company, a corporation of New York 11 Claims.

The invention relates to band ovens for baking biscuits, cookies and thelike, though Without limitation to any particular baked product, itsgeneral objects being to accomplish the baking process continuously,efficiently and at a high production rate. This application is adivision of our copending application Ser. No. 346,304, filed July 19,1940, and issued August 24, 1943, as Patent No. 2,327,727.

Inasmuch as baking requires the transfer to the goods of a definiteamount of heat and inasmuch as such transfer must occur within adefinite time period, it is obvious that the rate of production in bandovens depends on the length of the baking chamber or tunnel and thespeed with which the goods pass through it, that is to say, for a givencase, a longell band at higher speed gives the requisite baking periodwith a greater rate of production. One of the objects of this inventionhas reference to means of overcoming the mechanical difficulties whichhave heretofore limited band length and speed. These difficulties areprimarily incident to unexpected and non-uniform thermal expansions andcontractions which are increasingly manifest with longer bands makingthem exceedingly diflicult to keep under control at the higher speed.

Fig. 1 is an elevation, and Fig. 1a a plan, of the feed end of the newoven;

Fig. 2, an elevation and Fig. 2SL a plan, of a portion of the centralpart thereof Fig. 3, an elevation, and Fig. 3EL a plan, of the deliveryend;

Fig. 4, a larger scale side elevation of the drive head;

Figs. 5 and 6 are details of the burner construction;

Fig. 7 is a side elevation of the feed end;

Fig. 8, a plan thereof;

Fig. 9, a longitudinal vertical section of a portion of the tunnel nearthe feed end;

Fig. 10, a plan thereof;

Fig. 11, a cross section on line KiP-Xi of Fig. 1;

Fig. 12, a cross section on line XII- XII of Fig. 1;

Fig. 13 is a cross section of a portion of the tunnel Wall illustratingits laminated construction;

Fig. 14 is a cross section on line XIV-XIV of Fis. 9;

Fig. 15 is a cross section on line XV-XV of Fig. 14;

Fig. 16 is a cross section on Fig. 17 is a cross section on line XVII-XVII of Fie. 7;

Fig. 18 is a longitudinal section of the baking compartment section ofthe feed end of a band oven having a modied form of heat application;

Fig. 19 is a top plan thereof, partially broken out.

Fig. 20 is a Across section on line XX-XX of Fie. 19: Y

Fig. 21 is a section on line XXI- XXI of Fig. 19; and

Fig. 22 is a section on line XXII-XXII of Fig. 19. A

The oven proper consists of a baking chamber in the form of a tunnelbuilt of similar successive tunnel sections I supported in the upperparts of a series of upright external metal frames 2 rising ,from anysuitable foundation which however does not require to be a massivefoundation as usual because the Weight per foot is Well within ordinaryfactory floor load limits as later made apparent. These sections areconveniently about 8 feet long, and in the aggregate make a tunnel morethan and desirably about 500 feet which is much longer than hithertoconsidered practical for band ovens. The space below the floor of thetunnel is closed in by a series of panels 3, of insulating materialreferred to below. v

The endless baking band 4 is trained over a head or driving drum 5 atthe delivery end of the tunnel and a tail or take-up drum 6 at thedough-receiving or feeding end. Its upper run passes through the tunnelwhile its return run passes through the enclosed space under the tunnel,being suitably supported along the length of both runs as laterdescribed. This band is shown as an imperforate endless steel sheetapproximating 32 in width and .048" thickness in the present case and issu'iciently exible to be practicable for use on drums of reasonablysmall diameter as indicated but Within the term band is included alsoWoven-wire bands and any other conveyor suitable for supporting doughwhile baking. The direction of its travel is indicated by arrows.

The tail drum 6 (Figs. 7 and 8) is a tension and take-up drum, beingarranged to keep an appropriate and constant tension on the band at alltimes while also accommodating its very considerable change of lengthdue to temperature change, a matter of 3 feet or more according tocircumstances. For this purpose, the drum is journalled in a Wheeledtruck 1 running on rails 8 secured to the 'tops of two main girders 9which constitute part of the feed-end framework of the tunnel rigidlyaligned with it. The truck is subjectl to the pull of a twin cable lsupporting a suitable vWeight as the .means fof applying the tension.and the drum bearings =Il on the truck are adjustable by means of theset-bolts indicated so that the angle of the drum axle can be minutelychanged as required to counteract any tendency for the band toworkitself toward one side or other of its proper course. This adjustment ismade secure by` giving the truck a long wheel base on its rails and byusing `flanged wheels l2 which t the rails snugly thus to prohibit anylateral movement of the truck on the rails and insure that the closelyadjusted angle given to the drum will continue ypermanent as the lengthof the band changes under varying temperature.

The drum truck carries a clearer for the inner face of the band in theform of a plough i3 resiliently supported Ain any suitable way, thepurpose of which is to clear the band of any foreignmatter or objectwhich might interfere with traction or injure the band if caught'betweenit and-the drum. 'The methodof suspension comprises twospring-containing links I4 (Fig. 16) hung from the .truck to carry thewide end of ltheplough and a front link l5, also including a spring, tocarry the apex of the plough. This .link is hung from a cross yoke I6supported in part by the links I'A and by rollers vIII which run ontheinteriorlanges of the side girders 9. The springs in the Vlinkscounterpoise the plough so thatit floats orbears gently on the band,that is, with less thanits .full weight, thereby avoidingunnecessaryfriction and band Wear. fBeing carried'by the truck, the plough 4is`located at the end of the return runof the band and remains close .ftothe. drum under all thermal conditions.

The tail drum 6 is also tfurnished with a doctor knife 'I8 tokeep itclean. This is carried on the xed arms I9 and provided with a trough 20to catch the scrapings.V

The working runof .the band within the oven `tunnel rests on andisdriven vbythe upper .runs of a system of parallel endless steel cablesor wire ropes 2l which carry the 'heavyvertical load and lthe drivingtension. These cables-are trained over a set of drive sheaves`22 at thedelivery endand over a corresponding setof take-upand tensioning tailsheaves :23.at the :feed end and their return runs passibelow the tunnelvwhere theyare supported by a .number of 'intermediate sheaves vorcarriers presently referredto. 'The whole sys- Ltem is .located .withinthe conne Vof .the band, .between its upper and 'lower runs,and `theupper runs of the cables form-asupportiorthe band which .is co-extensivewith nearly-its full length and on which the upper'band-run rests withno other than frictional connection with it. The cables, it will heunderstood, are .essentially tension members which take the longitudinallstrain to which the band would Abe subject without them; theyconstitute 'thelmeans :whereby the long band `can be driven at therequiredhigh speed without injury to it; also they admit of the use.o'fwiremesh bands in ,'light'er weight .and'wider mesh -than heretoforepossible so'that morenearly equal top and bottom .bakingeffects on thegoods V.can `be produced, which fact substantially enlarges the field ofusevof band ovens.

The cable :tail ish-eaves 23 are journalled `side by side, but each,independently of therothers in a pairof slipper blocks' 24 .whichareconfined to slide in or-between'theopposing channels'offpar.-

4 allel I-beams 25 (Fig. 17), the latter being part of the feed-endframework carried on the side girders 9. The two blocks for each sheaveare connected'by a yoke 2B to `'ae-Weighted tension cable 21 which is,guided around the edges ofthe lower stretch of the band by appropriatecorner pulleys 128 so that the weights 29 can hang below and a the sideof the feed-end framework. The intermediate carrier sheaves abovereferred to are -marked 30, and occur in sets at fllpropriateintervalsalong the tunnel, preferably one set for each of the (8 foot) sections.The sheaves of each set are fast on axles 3l which extend across ,thetunnel and through the thickness Aof theztunnel lwalls to their bearings32 (Fig. .12) which are A,placed on the outside of the wall-wheretheyare not only accessible for lubrication but also suftcientlyremoved from oven heat so that the lubricant is not decomposed.

Since each cable is equally tensioned with the others their upper 4runsoccupy substantially a common level` and form va platform support forthe band whichis practically fiat. It is so indicated in therdrawing,.hutv actually and as will be understood, both the cables .and .band sagsomewhat between the carriers. It is desirable for high speed operationthat '.the `band make and preserve a continuous or line contact witheach one of the cables so far as possible and .this object isaccomplishedaccording to this invention partly by the .independence ofthe means for tensioning the .band andcables, thus permitting theappropriate tensioning force to be applied to each, and partly `by theselection ofan appropriate lateral separation ofthe cables.

This spacingis correlated to the crosswise flexibility of the band, sothat the latter can find a seat or bearing on .each cablenotwithstanding slight variations in their respective elevations. Itthus derives uniform driving force from each. In the case in hand, thespacing distance is about 81/2 inches requiring four cables -for asheet-steel band of the particular .weight and width employed. We havefound, however, that too wide a spacing is to be avoided since ittendsto bandfatigue under the loadr ofthe dough and too close spacing tends.to unbalance 'the contact, and hence to unequalized driving of thevband giving it a tendency to wanderffrom its course which must vat allcost be prevented. We ndthat the number of cables in the system must beselected with reference to the-establishment of continuous cable contactwith the band.

As also contributing to the uniformity and balance of the band drive,the tail sheave supports or slipper-blocks 24 are purposely loosely ttedin their slide-way channels in the beams 25 so that the sheaves arelfreeto change their angles slightly in accommodation to the angle ofapproach of the cables, whichat -times tend to deviate from normalproducing* momentary variation of the cable tension. `By .making eachtake-up sheave self-adjusting in .this way, the cables are best adaptedto .preserve continuous equal contact with the band so as to keep itrunning smoothly and in its true course notwithstanding' that Ait iswithoutymechanical attachment to them.

Also in this same connection, two of thefour cables are laid up with ahand or direction Kof twist opposite to that o f the other two, thusbalancing the tendency otherwise present for the cables to work the bandout of center.

` While the carrier sheaves v351| appear to be all of equal diameter itis preferred to make the two outside sheaves of each set of slightlylarger diameter, but not more than will raise the margins of the bandabout 11s above its center. gives the band a very slight crosswisecurvature which, though unperceptible to the eye, contributes stiffnessto the band against horizontal viiexure and thereby aids in keeping itin its straight course.

also preferably designed on the same principle.

The return carrier rollers 39 are These precautions are cumulativelyimportant factors in safely obtaining high speed of the long irregularlyexpanding band and eliminating the need for edge-guiding flanges orrollers within the tunnel which would be objectionable because, in ovenheat, they could not easily be kept lubricated and even thoughlubricated would result in wear or deformation of the edge of the band.

The return runs of the cables are carried `on a succession of carriersheaves 33 arranged in sets fast on axles 34 which are journalled belowthe tunnel floor but at the same time set high enough so that they aremore or less positively driven by the cables. Thus driven they aregeared by sprocket chains 35 to drive the cross shafts 35, journalledjust below them, which latter are provided with roll bosses 3'! andsupport the return stretch of the band helping it along by theirrotation.

The drum and driving sheaves are sprocketchain geared to a common shaft38, driven through a variable speed transmission 39 from an electricmotor 4! and these driving members are also disposed between the upperand lower runs of the band, that is to say, inside of the delivery endof the band and therefore out of the way of whatever means may beemployed for removing the baked goods. We have found that the head drum5 requires to be driven at a slightly higher circumferential speed thanthat of the driving sheaves 22 in order to insure that there shall be norelative movement between the band and the cables which conduces towandering of the band from its course.

With the construction described, all the guidance needed to keep thelong, flexible and high speed band running true on the cable system canbe accomplished by one, or at the most two, socalled automaticbelt-aligners. These are well known devices indicated conventionally at4l in Fig. 3. They can be placed outside of the oven and therefore belubricated and they Work with minimum friction on the band.

The baking heat is applied by a current of hot combustion gases flowinglongitudinally through the tunnel. In the case 0f the oven shown inFigs. 1-1'7, which is gas-fired, the current of hot gas is derived froma series of gas burners 42 of a type not heretofore used in band ovens.These burners are supplied with fuel-gas and air, both under slightpressure, to form a mixture which burns from the haring nozzles ,43 ofwhich there are several to each burner. By reason of the supplypressure, and principally by reason of the expansion in the nozzles, theflames are projected several inches from the burner orices, on whichaccount the burners are properly termed blast-type. They are arrangedcrosswise of the tunnel, with one four-nozzle burner above the band andone five-nozzle burner below the band in each tunnel section, al1projecting their names horizontally and in the same direction, so thatin the aggregate they create, by the effect of their own energy aturbulent baking current of considerable horizontal velocity, counter tothe direction of band travel,

This

`erned valve mechanism 44e subject to control by thermostatic bulbelements 44b located inside the tunnel (Fig. 12), the purpose being tomaintain automatically constant, pre-selected rates of heat transfer tothe goods.

The fuel system includes also a pilot ingition system (see Fig. 6)represented by the manifold tubes 41, one of which is common to all ofthe nozzles of each burner and supplied with a spark plug 48 to ignite aspecial explosive fuel mixture supplied to it through a pipe line 49.

The course through the baking tunnel is divided into a series ofcompartments each about 32 feet long, or otherwise as desired, and eachof which can thus be separately controlled as to temperature accordingto the requirements of the sort of goods to be baked, that is to say,each may have its own thermostat (44h) controlling the temperaturetherein according to the desired progress of the baking action. Thesecompartments are desirably separated from each other by interior bafflesor partitions such as indicated at 5i! in Fig. 9. The upper section ofeach partition includes a series of hinged flaps 5I (see Fig.k

14) which hang toward the top of the band and at its sides, and theseare so mounted that they may all be rocked to an open position whendesired by turning the shaft 52 by means of its exterior crank 53 alsoshown in Fig. 14, thereby enlarging the communication between adjacentcompartments.

Each tunnel compartment is provided with an exhaust outlet 54 by whichsteam, gases from the goods and products of combustion are withdrawn tothe exhaust manifold 55 by the suction of a fan 55 (Fig. 2) and in eachcase these outlets are located at the feed ends of the compartments fnext to the partitions 55, so that the fan suction assists the gascurrent through the tunnel, this being under the control of slidedampers at the outlets as indicated at 5l in Figs. 9 and 10.Irrespective of the partitions 50, it may be noted that thisdistribution of the exhaust outlets naturally divides the tunnel intobaking compartments in which the baking conditions as to heat andmoisture can be individually controlled.

As customary in band ovens the entrance and exit door-ways, at the endsof the tunnel, are protected by exhaust hoods 5B and 59 connected to theends of the exhaust manifold 55, so that combustion gases do not escapeinto the buildlng.

The baking tunnel is constructed of floor panels resting on longitudinalsills secured to the frame uprights 2, side-wall panels rising from thefloor panels within the upright, and roof panels spanning the sidewalls. The nature of the material used to form these panels exercises animportant influence on the operation of the oven as presently explained.Each panel is laminated of flat slabs 6i), cast of wetcementitiousmaterial which has been aerated before setting so that it sets as aporous, light and rigid slab and has sufficient strength to serve as astructural building element. Specifically the preferred material is agypsum plaster slab o-f which several types are to be had. A wallthickness of six one-inch slabs of this material is used for the sidewalls and closed. Inspection windows are also v.appropriate intervals.

.2a23-noo roof, and ionifsuice for the iloor, vthe `space ibelow thetunnel A:being .enclosed .as before stated. Baking .temperatures inthe.order of 50ll-.600.F. Aand the temperature `in the under-.tunnel spaceruns lat about 350 F. A similarslab Sais desir- Aably. used as the:floor -oftjhis space to insulate it from the building .floor asshowninFig. 12.

The tunnel shown is internally lined, more par- .ticularly as protectionagainst possible -mechanical injury, by thinner (1/20 slabs or sheets 6|of Hagenerally similar cementitious but harder material. The junctionsbetween sheets -are c overed with battens 62 ofthe same .material andvshort .corner braces 6.2'1-,arev'used inthe center of -eachsection tohold the Ipanels together.

It will be understood that Athe several panels are appropriately mounted'inl the framing With the necessary clearances to permit their thermal ynqnansion harmlessly.; also the individual lami- ;na`.tions of eachpanel are held together so that anydiierences in'their individualexpansions will :not .warp the panel.

n' K This is done 'by localizing .the uniting bolts (not shown) at themidportions [of `the panels, as Vwill be understood. Thus constructed,it is kto be noted that no metal is present in the ktunnel walls exceptfor the small corvvnerbrackets 62a and such bolts as unite the lami-.,nations.

The opening in the -roof shown at B2b in Fig. :9 is `an explosion ventnormally lightly provided at AInsuchan oven asabove described, heattransf er vto .thedough carried on the'band occursprincip'allybyconvection and conduction, and to only .a minor degree byradiation; that is to say, most of .the heat .units Vrequired for bakingare carried to Athe .dough directly by the stream of hot gas owing inthe tunnel in contact with it rather than by radiation from the walls of.the tunnel `and other bodies therein, such heat as is received 'by themetal band .passing by conduction through -the latter to the dough.-Heretofore radiant heat has beenchiefly relied on for the baking eifectin .band ovens, the radiation being from the walls ,and from numerousburners `or other heating.

elements located along the length .of the oven.

The relative suppression of radiant transfer a'iords the importantadvantage of a closer relation between the rate of fuel supply and thethermo-chemical change-that constitutes baking.

margins of the band from the radiant side-wall heat and therefore itdoes away completely with the need for marginal shields or otherprotectors for the goods such as have been heretofore resorted to inv.theveifort to secure an even bake kacross the band.

According to .the thermal law, the rate of heat transfer from hotgassesto other objects is proportional to the relative velocity of the gaswith respect to such objects, and therefore in the presentcase theconvection transfer of heat to the .goods occurs at arhgh rate becausethe relative Avelocity is high, being the sum of the gas velocity Vplusthat of the band speed, the latter being in the order of 10D feet ormore per minute. An optlmum condition for convection transfer to the.goods is thus established.

ySince all bodieshave the property of radiating .F.Osedgfcr taking upheat and therefore relatively less active asheat-'delivering surfaces.By taking advantage of this fact we have found that the radiant bakingeffect can :be reduced to such eX- tent, relatively -to the amount ofbaking heat transferred by convection and band conduction, Vas to makeits influence unobjectionable from the point of view of baking control.

The wall Vslabs of aerated plaster compound above referred to.-areselected .because they are Vnot Y.only good insulators but are oflow density and very low heat capacity being also very light. They weighin the order of less than 50 lbs.,per cubic foot. This is much lighterrthan fire-brick, building-brick, or even those iiocculent or lgranularinsulating materials commonly used as insulating filling betweenmetalcasement panels. Besides which these slabs have the advantage thattheir strength and rigidity, as already pointedout.

.enable the tunnel walls, including the roof, to be built of -themexclusively with the use of little or v.no metal, thereby producing asurrounding enclosure for the high-speed baking band 4having the leastpossible heat-radiating property.

.To the same `end of minimizing the heat capacity or radiant bakingeiect, all those metal parts inside the tunnel that .are incident to.the `transport of the goods .through it, as well as 'those parts whichconcern the distribution andow of the combustion gases, are made as lowin total massias consistent with their proper functioning. The combinedweight of the .steel band and the .four cables, for example, is lessthan 7 lbs. per

riers, although they .occur only at intervals, are

similarly .made of no more mass .than required fOr .their functions. asis true also .of Vthe burner.- bodies. Not counting the band, the wholetunnel-employs less than `30 lbs. of metal .per `linear foot of .tunnel(specifically 22.5 lbs). I'Ihe total .metal mass per foot will thus beseen to be extremely low as compared to prior .tunnels of 4comparablesection. For example, in a v.particular prior and well known type ofbandfoven, in which the walls are .metal lined as customary, the liningkalone .(ss" thick) weighs V3% lbs. .per square foot and .in theaggregate .such an oven contains 126.5

lbs. of metal per linear tunnel foot, Vnotcounting the conveyor member,all of which represents ja large .heat-radiating capacity. In priorstructures, when` adjustment is' made to reduce oven temperature theinterior kmetal parts act as Vsources of Aheat and delay the change, andlconversely, whenit issought to raise the oven temperature, they absorbheat and delay the eifect,

impractical the use ofithermostatic regulators for that purpose.` In thenew o ven, on the other hand,

having practically no. interior metal, and in which the dough issurrounded only by walls oflight weight. and low density and heatcapacity, the

time'lag is minimized to a degree that'is negligible and thermalregulationis thusmadegsoe fective that the progress of the bakingprocess can be automatically and continuously maintained according toany predetermined plan.

Referring to Figs. 18-22 the oven, band and cable system will berecognized as the same as that already described. The zone ofcombustion, however, is outside of the oven and in the form of a burner63, designed to burn'oil, for example, and operated by a motor-drivenfan 64, the burner detail not being important to this invention. Thereis one such burner for each baking compartment. It'delivers its hotcombustion products together with any excess air and perhaps other gasesdirectly into the intake flue 65 of a fan 66, driven by a motor 61,whence they are discharged at a selected temperature into a longitudinalflue above the tunnel having branched flues V|58 leading down the sidesof the tunnel with outlets into the tunnel respectively above and belowthe baking band and on both sides. The upper flue outlets 69 pass thehot gases, under appropriate damper regulation, as indicated, into aninternal duct 10 suspended from the tunnel roof and extending not morethan about half the length of the particular baking compartment. Thisduct can be made of light sheet metal if desired in which case its wallthickness willbe considerably thinner than indicated in the drawing. Inany case its heat capacity is low. Its floor is provided with many holesH (Fig. 19)

and occasional deflectors 12 slanted toward the holes.

The lower outlets 13 (Fig. 20), from the branched flues 68, pass thecombustion gases, also under appropriate damper control, into a similarlower internal duct 14 mounted on the floor of the tunnel.

The upper and lower ducts, 10 and 14, are provided withdamper-controlled outlets, 15, at their far ends, adjustable fromoutside the tunnel, and it will be recognized that the purpose of thisconstruction is to admit the gas-flow, so that it will not have tooviolent impact on the goods at its point of entry or tend to concentrateits heating eiect at any particular locality while at the same timeproducing the adequate longitudinal gas velocity which, as before, is ata high rate and counter to the band travel. By means of the dampers 15the velocity in the two ends of a compartment can be adjusted.

The gases leave the compartment by the outlet 1G which is represented inthe present case by three laterally separated hoods 16 let into thetunnel roof and leadingthrough a single return iiue l1, on the tunneltop back to the place of combustion or burner 63. There is thus a closedcombustion circuit, including the tunnel compartment and enough air asmay be required for combustion is delivered into this circuit by the fan64, while a constant excess of tunnel gases, steam, etc. is beingevacuated through the suction exhaust outlets 54 and manifold 55.

The tunnel walls will be understood to be of the same light weight andlow heat capacity as above described and it may be stated that theinterior distributing ducts, when made of metal, do not add appreciablyto the total mass of exposed metal per tunnel foot, since they are insubstitution for the metal burner and pilot system used as the heatsource in the gas-fired oven and not used in this form. The thermalcharacteristics are therefore the same as in the gasred form and aresuch as to insure that the baking occurs mainly by convection and leastby 10 radiation and therefore with the advantages above pointed out.

It will be understood that within the principles above explained,band-ovens can be constructed in many Variant forms and of any lengthrequired and that there is no intended limitation to either of the formsherein used. for exemplication, nor to any of the detail thereof exceptas specied in certain of the claims.

We claim:

1. In a band oven, an endless baking band trained over a drum at eachend of the baking tunnel, one of the drums being journalled on a truck,a guiding track for the truck conning it to move only in a directionparallel with the tunnel axis, means for angularly adjusting the drumaxis with reference to such truck and means for applying constantband-tensioning force tov to such truck and means for applying aconstant tensioning force to the truck,

3. A bakers band oven, a tunnel, a flat steel baking band, and a cablesystem carrying and frictionally driving the working stretch of the flatband through the tunnel comprising a plurality of parallel cables someof which are of opposite hand of twist to the others, and independenttensioning means for the cable stretches adapted for maintaining them incontact with the band under changing oven temperature.

4. In a bakers band oven comprising a baking tunnel and anendlessrsubstantially at sheet metal baking band having its workingstretch running through the tunnel, means for supporting and drivingsaid working stretch in the tunnel comprising a system of parallelendless cable stretches, auto-matic take-up means for maintaining saidstretches at a substantially common elevation whereby said flat bandrests uniformly upon them and another automatic take-up means for saidband adapted to take up thermal changes in the length thereof, and meanswholly outside the tunnel for guiding the course of the band againstlateral deviation.

5. In a band oven, a conveyor structure comprising` a system ofparallel, separated stretches of metallic cable supported at a commonlevel and individually tensioned to maintain such level while inaction,an endless sheet-metal band of substantially flat cross-section havingits working stretch resting on such cable stretches and having only afriction contact therewith for maintaining its position thereon, headand tail drums over which said band is trained under constant tension,head and tail sheaves for said cable stretches located in the spacebetween the runs of the band, and means for guiding the course of theband located adjacent to one of said drums and wholly outside of theoven in which the band travels.

6. In a band oven, a conveyor structure comprising a system of parallel,separated stretches of metallic cable supported at a common level andindividuallytensi'oned to; maintain such level having only' a frictioncontact therewith forA maintaining its positionthereon, head and taildrums:` over' which saicfbandi is' trained: under* constant tension,head.: and tail sheaves-for said cable stretches located: in the spacebetween theA set ofV sheaves being-locatedadjacent one of' saidvdrumsand the otherset being located-'adjacent theotherV d-I'lim, endlesscables trained over said sheaves and! each of saidlcableshaving at leastone run within said tunnel, saidfrun of the metal bandresting on and`beingsupported by the saidruns of' saidcabl'es, a journall bearing'. foreach of said-sheavesof one ofithe said sets, guides for each of-"sai'djournal bearingsV located` between the runsof said band and' extendingparallel to the bandi, said bearings being slidabiein-sai'd guides-lindependently one of another, andi-meansfor applying tension to saide--d-less.cablescbmprising a-tension cable 'connected-to each of saidjournalbearings, guide meanslr directing; each of saidtension cablesfromitsjournal'bearing parallel to said band` andthencefoutw'ard frombetween the' runsof said band; and a tensioning means for! each-of saidtension cables located 'outside of the said band.'

8. In a-fband, oven, a; bakingtunnel, a drum journaledateacli endvofsaidw tunnel, an endless substantiallyatimetal. band trainedover said.`

drums and having-fat least, oneof itsruns dis-A posed withinsaid tunnel,and meansttofsupport saidirun ofdzhe metal bandrwithinlthe-tunnel complising two sets offcable sheaves-,located between the4 two=- runs of',said band. and; between said drums; one'Y set offV sheaves:being-located adjacent one of said; drums andjthe;otherset beingllocated. adjacent; the: othericlrum, endless cables trained over:said-sheaves and yeach of said 'cables having-at' leastone 1un":withii'isaid tunnel, said run of the metal'band-irestingoniand beingsupported bythe said runs of-said` cables, bearing means for the sheavesof oneof-the said sets substantially xedin position, powermeans to drivethe'sheavesof' said-` set, a journal bearingfor each ofrthe sheavesoithe other of said sets, guides for eacli. ofv said journal bearingsVlocated between;

12y the. runs of'saigd band andV eliteudine parallel to* the: band;saide bearings-l beingf slidable in said guidesv indenendentlyl one oianother?, andmeans;- for applying,- tensicm'.` tei-said endless?cablescomprising a tension cablefconnec-tedto each-of said;`

jour-nal bearings,` guidef'means'- directing:` each;V of; saidf tensioncables imm its journal bearingpar-,- allel torsaid band; andthenceoiitward from" bei-.- tween. the runsof said? bandi.. andV a.tensioning; means for each of;l said tension: cables locatedVV outsideof the said-, band,.-l

9'.; 'Ehe subject-matter oi claim 7;, c lslarac t-erized;A bythe tactthat. the; runs of theendlesscablesv` within the; tunnel are; supprted;at, a-A common-g level, and meansareprovidedzor. conjointly drive.- ingthe endless` cablefsystemand; the head drinnV ot saidl band. i

10; 'Ehe subject. matterA of elarir'sJ Character-- ized by the, fact'that the saidjour-nal bearings: are loosely mounted? thef-saicl-v guidesso that thesheaves ofthe said-setfca-n turn' angular-ly toaecommodatethe angleeof: approaehrcf their re-4 spective endless cables;

1 1. Ina ban-doven; abakingtunnel-,aframe structure fixed atAone'endfothe-tunnelr andf includinghorizontal beams L sro-vid-ing.-upperguide'-` ways and a lower ,fg-uideway;4 said? guideWay-s` ex@ tendinginthe saine;-V directionas said-ftunnel, a truck movable cnrs-aidlower-.guidewa-y; drums at opposite ends off theftunneli. one: off saiddrumsjl beine.' journaled on` said:V trucle, a bakingband-- carriedbysaid drums and passing through said-` tunnel, a set. oifcable sheavesatieach; end? of; said tunnel, bearings-for the sheaves"- forone-o? saidsetsmovable in-said-upperguideways, band-@supepcrting cables carried bythesaid sheaves; and means tending to move said truokandrsaidbeaningsa-longl said guideways A to' tensionsaid band arlldfcables D:- LOGSE; l

' Wi W-ATKNS.-

aEEEENCas; ouen" The icllowingreferences are of-recordinfthe iY leoivthis'v patent UN'lED STATES Pa'rfiiNTsf 1,313,111- Aug. 12, 19191,493,619: .Lune 10; 1924. 1,626,041 --Apra 26, 1927" 1,667,765- May- 1,1928- 1,67.-9,7'1-7 A ,-Aug. 7;- 192& 1-,726g-555 Gammeter j- Sept.3;.l929f 1,933,485 yRund etal. -1-, Oct-.31, 1933- 1,970,8&2. Crossen.Aug. 2,1, 1934- 1,9i71,'166.- Byron et al -1.11. Aug. 28, 19341,975,591Y Sinden ,1.-- Oct.-v 2', 1934- 2,157,301.

Neuman Mayy 9, 1939

